As one of mounting techniques for a semiconductor chip, there is a technique called a flip chip scheme. According to the flip chip scheme, protrusive electrodes (bumps) 31 are formed on the surface of a semiconductor chip 30, and the bumps 31 are directly connected to electrode pads 32 on a substrate 29.
In the flip chip packaging, a resin is filled into a gap between the semiconductor chip 30 and the substrate 29 for reinforcement of a connecting portion 33 in order to prevent that stress generated due to difference in thermal expansion coefficient between the semiconductor chip 30 and the substrate 29 concentrates on the connecting portion 33 and damages the connecting portion 33. Such a process is called “underfilling” (see FIG. 7).
The underfilling process is performed by applying a liquid resin 34 along an outer periphery of the semiconductor chip 30, filling the resin 34 into the gap between the semiconductor chip 30 and the substrate 29 based on a capillary action, and then heating and hardening the resin 34 in an oven, for example.
In the underfilling process, it is required to consider change in viscosity of a resin material with the lapse of time. This is because there is a problem that as viscosity increases, an amount of material ejected through a discharge port reduces and the capillary action is insufficient, whereby the material is not filled in a proper amount into the gap. In the case of the viscosity changing to a large extent, the ejection amount reduces 10% or more after 6 hours, for example. This results in the necessity of correcting the change of the ejection amount, which is caused by the viscosity change with the lapse of time.
In general, a dispenser is used to fill the resin material in the underfilling process. As one type of dispenser, there is a jet type dispenser for ejecting the liquid material in the form of jetted small droplets from a nozzle.
A method of performing the underfilling process using the jet type dispenser is disclosed in, for example, Japanese Patent Laid-Open Publication No. 2004-344883 (Patent Document 1). In more detail, Patent Document 1 discloses a method of ejecting a viscous material onto a substrate by employing the jet type dispenser, the method comprising the steps of previously confirming a total volume of the viscous material to be ejected and a length over which the viscous material in the total volume is ejected, performing an operation to apply a plurality of liquid droplets of the viscous material onto a weighing gauge, generating a feedback signal representing the weight of the plural liquid droplets of the viscous material having been applied onto the weighing gauge, and determining a maximum relative speed between the dispenser and the substrate such that the viscous material in the total volume is ejected over the aforesaid length.
The method disclosed in Patent Document 1 further comprises the steps of determining respective volumes of the plural droplets of the viscous material, determining a total number of liquid droplets, which is required to provide a volume of the viscous material substantially equal to the total volume, determining a distance between the liquid droplets, which is required to substantially uniformly distribute the liquid droplets of the viscous material over the aforesaid length, and determining a rate value at which the liquid droplets of the viscous material are ejected from the dispenser to eject the viscous material in the total volume over the aforesaid length at the maximum relative speed.
Moreover, when the underfilling is performed, a fillet portion 35 filled with the liquid resin 34 is formed at a corner defined by a lateral surface of the semiconductor chip 30 and the substrate 29. The fillet portion 35 is called a “fillet” (see FIG. 8). If the fillet 35 is non-uniformly formed, problems arise in that air may enter through a portion where the fillet 35 is small, thus causing entrapment of bubbles, that the resin 34 may extend to enter an application inhibited region around a chip 30 as an application target, and that a semiconductor chip 34 may be damaged in the heating and hardening step. For that reason, the fillet 35 is required to be uniformly formed with a constant width 36 and a constant height 37.
One cause why the fillet 35 is non-uniformly formed resides in a difference in degree of penetration depending on density at which the bumps 31 are arranged. In general, the liquid resin 34 penetrates more quickly at a location where the bumps 31 are arranged at a higher density, and the liquid resin 34 penetrates more slowly at a location where the bumps 31 are arranged at a lower density. Therefore, when the liquid resin is applied in a constant amount, the fillet 35 being not uniform in the width 36 and the height 37 is formed depending on the above-mentioned difference in degree of penetration, and the shape of the fillet 35 becomes not uniform.
Another cause why the fillet 35 is non-uniformly formed resides in speed change during the application operation. When the application is performed along an L- or U-shaped locus that requires a moving direction of the dispenser to be changed, a moving speed has to be reduced at a corner (direction changing portion) for change of the direction. Furthermore, the moving speed has also to be reduced at the start and the end of movement of the dispenser. Such a speed reduction is unavoidable because the dispenser is a mechanical machine. Thus, when the liquid resin is applied in the constant amount, the application amount is increased at the corner, the start point, and the end point, whereby the shape of the fillet 35 becomes not uniform.
In addition, the following technique is known as another example of the technique for applying the liquid material in the underfilling process.
Patent Document 2 discloses an application method of preparing a desired application pattern, ejecting a liquid material from a nozzle while a nozzle and a workpiece are moved relative to each other, and applying the liquid material in a specified amount to the workpiece, the application method comprising a step of specifying, as a total pulse number, the number of times ejection pulses or pause pulses are transmitted, specifying the number of ejection pulses required to achieve the ejection amount, and specifying a remaining pulse number as the number of pause pulses; a step of measuring an amount of the liquid material ejected from the nozzle at timing of a preset correction period, and calculating a correction amount of the ejection amount; and a step of adjusting the number of ejection pulses and the number of pause pulses based on the calculated correction amount.
Patent Document 3 discloses a liquid material filling method for filling, based on a capillary action, a liquid material ejected from an ejection device into a gap between a substrate and a workpiece placed on the substrate, the method comprising the steps of preparing an application pattern made up of a plurality of continuous application regions, allocating a plurality of ejection cycles to the application regions, the cycles each including ejection pulses and pause pulses combined at a predetermined ratio between respective pulse numbers, measuring an amount of the liquid material ejected from the ejection device at timing of a preset correction period, and calculating a correction amount of the ejection amount, the method further comprising a step of adjusting the number of ejection pulses and the number of pause pulses, both included in the application pattern, based on the calculated correction amount, and/or a step of adjusting a length of at least one of the application regions and a length of one or two of the application regions, the latter one or two application regions being continuous to the former one application region, without changing the ejection amount in each of the application regions per unit time.